Organic electroluminescent device

ABSTRACT

An organic electroluminescent device includes a pair of electrodes; and an organic layer between the pair of electrodes, which includes a light-emitting layer, wherein the organic layer contains a compound represented by the following formula (I); and the light-emitting layer contains a iridium complex phosphorescent material: 
                         
wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7  and R 8  each represents a hydrogen atom or a substituent, and contiguous substituents of R 1  to R 8  may be bonded to each other to form a condensed ring; R 9  represents an alkyl group, an alkenyl group, an aryl group, a hetero-aryl group, or a silyl group, and each of which group may be substituted with a substituent; and at least one of R 1  to R 9  represents a deuterium atom or a substituent containing a deuterium atom.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/142,509, filed on Apr. 29, 2016, now allowed, which is adivisional of U.S. patent application Ser. No. 12/122,059, filed on May16, 2008, now allowed, which claims priority to Japanese ApplicationNos. JP 2007-133112, filed May 18, 2007, and JP 2008-105096, filed Apr.14, 2008, all of which applications are incorporated by reference hereinin their entireties.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an organic electroluminescent devicecapable of emitting light by converting electric energy into light(hereinafter also referred to as “organic EL device”, “luminescentdevice” or “device”), in particular relates to an organicelectroluminescent device excellent in light-emitting characteristicsand durability.

2. Description of the Related Art

Various types of display devices using organic light-emitting materials(organic luminescent devices) are actively researched and developedthese days. Above all, organic EL devices are attracting publicattention as promising display devices for capable of emitting light ofhigh luminance with low voltage.

Also in recent years, the increase in efficiency of the devices has beenadvanced by the use of phosphorescent materials. As phosphorescentmaterials, iridium complexes and platinum complexes are known. (Refer toU.S. Pat. No. 6,303,238, WO 00/57676 and WO 00/70655.)

A light-emitting layer comprising the combination of Ir(ppy)(iridium-tris(phenylpyridine)) as the dopant and CBP(4,4′-dicarbazolebiphenyl) as the host material is disclosed in patentdocument 3.

In WO 02/047440, an organic compound containing a deuterium atom isused, but there is no description in the same patent in connection withthe effect in using the organic compound in combination with aphosphorescent metal complex material.

A carbazole material containing a deuterium atom having phosphorescenceat ordinary temperature is used in JP-A-2005-48004 (The term “JP-A” asused herein refers to an “unexamined published Japanese patentapplication”), but there is no description in the same patent inconnection with the effect in using the material in combination with aphosphorescent metal complex material.

SUMMARY OF THE INVENTION

The invention provides a luminescent device excellent in efficiency(electric power consumption) and durability.

The above has been achieved by the following means,

<1> An organic electroluminescent device comprising:

a pair of electrodes; and

an organic layer between the pair of electrodes, which comprises alight-emitting layer,

wherein the organic layer contains a compound represented by thefollowing formula (I); and

the light-emitting layer contains a iridium complex phosphorescentmaterial:

wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each represents a hydrogen atom or asubstituent, and contiguous substituents of R¹ to R⁸ may be bonded toeach other to form a condensed ring;

R⁹ represents an alkyl group, an alkenyl group, an aryl group, ahetero-aryl group, or a silyl group, and each of which group may besubstituted with a substituent; and

at least one of R¹ to R⁹ represents a deuterium atom or a substituentcontaining a deuterium atom.

<2> The organic electroluminescent device of <1>, wherein

the iridium complex phosphorescent material has a maximum emissionwavelength of smaller than 470 nm.

<3> The organic electroluminescent device of <1>, wherein

the iridium complex phosphorescent material contains a ligand bonding toan iridium atom via a carbene carbon.

<4> The organic electroluminescent device of <3>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via a carbene carbon is represented by the followingformula (II):

wherein

R²¹, R²², R²³, R²⁵, R²⁶, R²⁷ and R²⁸ each represents a hydrogen atom ora substituent;

L²¹ represents a ligand;

n²² represents an integer of from 1 to 3;

n²¹ represents an integer of from 0 to 4; and

C represents the carbene carbon coordinating to the iridium atom.

<5> The organic electroluminescent device of <4>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via a carbene carbon is represented by the followingformula (III):

wherein

R³¹ represents an alkyl group or an aryl group;

R³⁵, R³⁶ and R³⁷ each represents a hydrogen atom, a fluorine atom, analkyl group, or a cyano group, and R³⁵ and R³⁶ or R³⁶ and R³⁷ may bebonded to each other to form a condensed ring structure;

L³¹ represents a ligand;

n³² represents an integer of from 1 to 3;

n³¹ represents an integer of from 0 to 4; and

C represents the carbene carbon coordinating to the iridium atom.

<6> The organic electroluminescent device of <1>, wherein

the iridium complex phosphorescent material contains a ligand bonding toan iridium atom via a nitrogen atom of a pyrazole structure.

<7> The organic electroluminescent device of <6>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via a nitrogen atom of a pyrazole structure isrepresented by the following formula (IV):

wherein

R⁴¹, R⁴², R⁴³, R⁴⁵, R⁴⁶, R⁴⁷ and R⁴⁸ each represents a hydrogen atom ora substitutent;

L⁴¹ represents a ligand;

n⁴² represents an integer of from 1 to 3; and

n⁴¹ represents an integer of from 0 to 4.

<8> The organic electroluminescent device of <7>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via a nitrogen atom of a pyrazole structure isrepresented by the following formula (V):

wherein

R⁵² and R⁵³ each represents a hydrogen atom, an alkyl group, or an arylgroup;

R⁵⁵, R⁵⁶ and R⁵⁷ each represents a hydrogen atom, a fluorine atom, analkyl group, or a cyano group, and R⁵⁵ and R⁵⁶ or R⁵⁶ and R⁵⁷ may bebonded to each other to form a condensed ring structure;

L⁵¹ represents a ligand;

n⁵² represents an integer of from 1 to 3; and

n⁵¹ represents an integer of from 0 to 4.

<9> The organic electroluminescent device of <1>, wherein

the iridium complex phosphorescent material contains a ligand bonding toan iridium atom via the nitrogen atom of a pyridine structure.

<10> The organic electroluminescent device of <9>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyridine structure isrepresented by the following formula (VI):

wherein

R⁶¹, R⁶², R⁶³, R⁶⁴, R⁶⁵, R⁶⁶, R⁶⁷ and R⁶⁸ each represents a hydrogenatom or a substituent;

L⁶¹ represents a ligand;

n⁶² represents an integer of from 1 to 3; and

n⁶¹ represents an integer of from 0 to 4.

<11> The organic electroluminescent device of <10>, wherein

the iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyridine structure isrepresented by the following formula (VII):

wherein

R⁷³ represents a hydrogen atom, an alkyl group, an amino group, or analkoxyl group;

R⁷⁵, R⁷⁶ and R⁷⁷ each represents a hydrogen atom, a fluorine atom, acyano group, or an alkyl group;

L⁷¹ represents a ligand;

n⁷² represents an integer of from 1 to 3; and

n⁷¹ represents an integer of from 0 to 4.

<12> The organic electroluminescent device according to <1>, wherein

the compound represented by formula (I) is represented by the followingformula (VIII):

wherein

R⁸¹, R⁸², R⁸³, R⁸⁴, R⁸⁵, R⁸⁶, R⁸⁷ and R⁸⁸ each represents a hydrogenatom or a substituent, and contiguous substituents of R⁸¹ to R⁸⁸ may bebonded to each other to form a condensed ring structure;

A represents a linking group; and

n⁸¹ represents an integer of from 2 to 6; and

the compound represented by the formula (VIII) contains at least onedeuterium atom.

<13> The organic electroluminescent device of <1>, wherein

the compound represented by the formula (I) is contained in thelight-emitting layer.

DETAILED DESCRIPTION OF THE INVENTION

The organic electroluminescent device of the invention (hereinaftersometimes referred to as “the device of the invention”) is an organicelectroluminescent device comprising a pair of electrodes and at leastone organic layer (the organic layer may be a layer comprising anorganic compound alone, or may be an organic layer containing aninorganic compound) including a light-emitting layer between the pair ofelectrodes, and any of the organic layers contains at least one compoundrepresented by the following formula (I), and the light-emitting layercontains at least one iridium complex phosphorescent material.

The compound represented by formula (I) of the invention is excellent inchemical stability, hardly accompanied by decomposition of the materialduring driving of the device, and capable of preventing reduction ofefficiency and reduction of duration of life of the organicelectroluminescent device using the iridium complex phosphorescentmaterial due to the decomposed product.

The compound represented by formula (I) will be described below.

In formula (I), R¹ to R⁸ each represents a hydrogen atom or asubstituent, and contiguous substituents of R¹ to R⁸ may be bonded toeach other to form a condensed ring; R⁹ represents an alkyl group, analkenyl group, an aryl group, a hetero-aryl group, or a silyl group, andeach group may be substituted with a substituent, and at least one of R¹to R⁹ represents a deuterium atom or a substituent containing adeuterium atom.

The substituents represented by R¹ to R⁸ are not especially restricted.For example, an alkyl group, an alkenyl group, an alkynyl group, an arylgroup, a hetero-aryl group, an amino group, an alkoxyl group, an aryloxygroup, a heterocyclic oxy group, an acyl group, an alkoxycarbonyl group,an aryloxycarbonyl group, an acyloxy group, an acylamino group, analkoxycarbonylamino group, an aryloxycarbonylamino group, asulfonylamino group, a sulfamoyl group, a carbamoyl group, an alkylthiogroup, an arylthio group, a heterocyclic thio group, a sulfonyl group, asulfinyl group, a ureido group, a phosphoric acid amido group, ahydroxyl group, a mercapto group, a halogen group, a cyano group, asulfo group, a carboxyl group, a nitro group, a hydroxamic acid group, asulfino group, a hydrazino group, an imino group, a heterocyclic group,a silyl group, a silyloxy group, a deuterium atom, etc., areexemplified. These substituents may further be substituted with othersubstituent, and these substituents may be bonded to each other to forma ring.

The alkyl group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 10 carbon atoms, and, e.g., methyl, ethyl, n-propyl, isopropyl,n-butyl, tert-butyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, n-octadecyl,n-hexadecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cyclooctyl, 1-adamantyl, trifluoromethyl, etc., are exemplified.

The alkenyl group has preferably from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 10 carbon atoms, and, e.g., vinyl, allyl, 1-propenyl, 1-isopropenyl,1-butenyl, 2-butenyl, 3-pentenyl, etc., are exemplified.

The alkynyl has preferably from 2 to 30 carbon atoms, more preferablyfrom 2 to 20 carbon atoms, and especially preferably from 2 to 10 carbonatoms, and, e.g., ethynyl, propargyl, 1-propynyl, 3-pentynyl, etc., areexemplified.

The aryl group has preferably from 6 to 30 carbon atoms, more preferablyfrom 6 to 20 carbon atoms, and especially preferably from 6 to 12 carbonatoms, and, e.g., phenyl, o-methylphenyl, m-methylphenyl,p-methylphenyl, 2,6-xylyl, p-cumenyl, mesityl, naphthyl, anthranyl,etc., are exemplified.

The hetero-aryl group has preferably from 1 to 30 carbon atoms, and morepreferably from 1 to 12 carbon atoms, and the hetero-atoms are, e.g., anitrogen atom, an oxygen atom, and a sulfur atom, specifically, e.g.,imidazolyl, pyrazolyl, pyridyl, pyrazyl, pyrimidyl, triazinyl, quinolyl,isoquinolyl, pyrrolyl, indolyl, furyl, thienyl, benzoxazolyl,benzimidazolyl, benzothiazolyl, carbazolyl, azepinyl, etc., areexemplified.

The amino group has preferably from 0 to 30 carbon atoms, morepreferably from 0 to 20 carbon atoms, and especially preferably from 0to 10 carbon atoms, and, e.g., amino, methylamino, dimethylamino,diethylamino, benzylamino, diphenylamino, ditolylamino, etc., areexemplified.

The alkoxyl group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 10 carbon atoms, and, e.g., methoxy, ethoxy, butoxy, 2-ethylhexyloxy,etc., are exemplified.

The aryloxy group has preferably from 6 to 30 carbon atoms, morepreferably from 6 to 20 carbon atoms, and especially preferably from 6to 12 carbon atoms, and, e.g., phenyloxy, 1-naphthyloxy, 2-naphthyloxy,etc., are exemplified.

The heterocyclic oxy group has preferably from 1 to 30 carbon atoms,more preferably from 1 to 20 carbon atoms, and especially preferablyfrom 1 to 12 carbon atoms, and, e.g., pyridyloxy, pyrazyloxy,pyrimidyloxy, quinolyloxy, etc., are exemplified.

The acyl group has preferably from 2 to 30 carbon atoms, more preferablyfrom 2 to 20 carbon atoms, and especially preferably from 2 to 12 carbonatoms, and, e.g., acetyl, benzoyl, formyl, pivaloyl, etc., areexemplified.

The alkoxycarbonyl group has preferably from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 12 carbon atoms, and, e.g., methoxycarbonyl, ethoxycarbonyl, etc.,are exemplified.

The aryloxycarbonyl group has preferably from 7 to 30 carbon atoms, morepreferably from 7 to 20 carbon atoms, and especially preferably from 7to 12 carbon atoms, and, e.g., phenyloxycarbonyl, etc., are exemplified.

The acyloxy group has preferably from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 10 carbon atoms, and, e.g., acetoxy, benzoyloxy, etc., areexemplified.

The acylamino group has preferably from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 10 carbon atoms, and, e.g., acetylamino, benzoylamino, etc., areexemplified.

The alkoxycarbonylamino group has preferably from 2 to 30 carbon atoms,more preferably from 2 to 20 carbon atoms, and especially preferablyfrom 2 to 12 carbon atoms, and, e.g., methoxycarbonylamino, etc., areexemplified.

The aryloxycarbonylamino group has preferably from 7 to 30 carbon atoms,more preferably from 7 to 20 carbon atoms, and especially preferablyfrom 7 to 12 carbon atoms, and, e.g., phenyloxycarbonylamino, etc., areexemplified.

The sulfonylamino group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., methanesulfonylamino,benzenesulfonylamino, etc., are exemplified.

The sulfamoyl group has preferably from 0 to 30 carbon atoms, morepreferably from 0 to 20 carbon atoms, and especially preferably from 0to 12 carbon atoms, and, e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl, etc., are exemplified.

The carbamoyl group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., carbamoyl, methylcarbamoyl,diethylcarbamoyl, phenylcarbamoyl, etc., are exemplified.

The alkylthio group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., methylthio, ethylthio, etc., areexemplified.

The arylthio group has preferably from 6 to 30 carbon atoms, morepreferably from 6 to 20 carbon atoms, and especially preferably from 6to 12 carbon atoms, and, e.g., phenylthio, etc., are exemplified.

The heterocyclic thio group has preferably from 1 to 30 carbon atoms,more preferably from 1 to 20 carbon atoms, and especially preferablyfrom 1 to 12 carbon atoms, and, e.g., pyridylthio, 2-benzimidazolylthio,2-benzoxazolylthio, 2-benzothiazolylthio, etc., are exemplified.

The sulfonyl group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., mesyl, tosyl, trifluoromethanesulfonyl,etc., are exemplified.

The sulfinyl group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., methanesulfinyl, benzenesulfinyl, etc.,are exemplified.

The ureido group has preferably from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, and, e.g., ureido, methylureido, phenylureido, etc.,are exemplified.

The phosphoric acid amido group has preferably from 1 to 30 carbonatoms, more preferably from 1 to 20 carbon atoms, and especiallypreferably from 1 to 12 carbon atoms, and, e.g., diethylphosphoric acidamido, phenylphosphoric acid amido, etc., are exemplified.

As the halogen atoms, e.g., a fluorine atom, a chlorine atom, a bromineatom, an iodine atom, etc., are exemplified.

The heterocyclic group has preferably from 1 to 30 carbon atoms, andmore preferably from 1 to 12 carbon atoms, and the hetero-atoms are,e.g., a nitrogen atom, an oxygen atom, and a sulfur atom, specifically,e.g., piperidyl, morpholino, pyrrolidyl, etc., are exemplified.

The silyl group has preferably from 3 to 40 carbon atoms, morepreferably from 3 to 30 carbon atoms, and especially preferably from 3to 24 carbon atoms, and, e.g., trimethylsilyl, triethylsilyl,triisopropylsilyl, dimethyl-tert-butylsilyl, dimethylphenylsilyl,diphenyl-tert-butylsilyl, triphenylsilyl, tri-1-naphthylsilyl,tri-2-naphthylsilyl, etc., are exemplified.

The silyloxy group has preferably from 3 to 40 carbon atoms, morepreferably from 3 to 30 carbon atoms, and especially preferably from 3to 24 carbon atoms, and, e.g., trimethylsilyloxy, triphenylsilyloxy,etc., are exemplified.

As the substituents represented by R¹ to R⁸, a deuterium atom, an alkylgroup, an aryl group, a hetero-aryl group, a halogen group, a cyanogroup, and a silyl group are preferred, a deuterium atom, an alkylgroup, a hetero-aryl group, a halogen group, a cyano group, and a silylgroup are more preferred, and a deuterium atom, an alkyl group, ahetero-aryl group, and a silyl group are especially preferred. Thesesubstituents may further be substituted with other substituent, andthese substituents may be bonded to each other to form a ring.

As the alkyl groups represented by R¹ to R⁸, the preferred are methyl,ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-octyl, cyclopropyl,cyclopentyl, cyclohexyl, 1-adamantyl, and trifluoromethyl, the morepreferred are methyl, isopropyl, tert-butyl, n-octyl, cyclopentyl,cyclohexyl, 1-adamantyl, and trifluoromethyl, and the especiallypreferred are tert-butyl, cyclohexyl, 1-adamantyl, and trifluoromethyl.These substituents may further be substituted with other substituent,and these substituents may be bonded to each other to form a ring.

As the hetero-aryl groups represented by R¹ to R⁸, the preferred areimidazolyl, pyrazolyl, pyridyl, quinolyl, isoquinolyl, pyrrolyl,indolyl, furyl, thienyl, benzoxazolyl, benzimidazolyl, benzothiazolyl,carbazolyl, and azepinyl, the more preferred are imidazolyl, pyrazolyl,quinolyl, indolyl, furyl, thienyl, benzimidazolyl, carbazolyl, andazepinyl, and the especially preferred are indolyl, furyl, thienyl,benzimidazolyl, carbazolyl, and azepinyl. These substituents may furtherbe substituted with other substituent, or may form a condensed ringstructure, or these substituents may be bonded to each other to form aring.

As the silyl groups represented by R¹ to R⁸, the preferred aretrimethylsilyl, triethylsilyl, triisopropylsilyl,dimethyl-tert-butylsilyl, dimethylphenylsilyl, methyldiphenylsilyl,diphenyl-tert-butylsilyl, and triphenylsilyl, the more preferred aretrimethylsilyl, triisopropylsilyl, dimethyl-tert-butylsilyl,diphenyl-tert-butylsilyl, and triphenylsilyl, and the especiallypreferred are trimethylsilyl, dimethyl-tert-butylsilyl, andtriphenylsilyl. These substituents may further be substituted with othersubstituent, and these substituents may be bonded to each other to forma ring.

As the substituents represented by R² and R⁷, the preferred are an alkylgroup, an aryl group, a silyl group, and a deuterium atom, the morepreferred are an alkyl group, a silyl group and a deuterium atom, andthe especially preferred are a tert-butyl group, an adamantyl group, atrimethylsilyl group, a triphenylsilyl group, and a deuterium atom.

As the substituents represented by R³ and R⁶, the preferred are an alkylgroup, an aryl group, a silyl group, and a deuterium atom, the morepreferred are an alkyl group, a silyl group and a deuterium atom, andthe especially preferred are a tert-butyl group, an adamantyl group, atrimethylsilyl group, a triphenylsilyl group, and a deuterium atom.

The specific examples of the combinations of substituents represented byR¹ to R⁸ are shown below, but the invention is not restricted to thesecompounds. In the structural formulae, D represents a deuterium atom.

For example, in formula (a-0), all of R¹ to R⁸ represent a hydrogenatom, in formula (a-1), all of R¹, R², R⁴, R⁵, R⁷ and R⁸ represent ahydrogen atom, and R³ and R⁶ represent a deuterium atom, and in formula(a-4), all of R¹ to R⁸ represent a deuterium atom.

Incidentally, formulae (a-0) to (k-0) (not containing a deuterium atom)do not satisfy formula (I), but formulae other than the above satisfyformula (I).

R⁹ represents an alkyl group, an alkenyl group, an aryl group, ahetero-aryl group, or a silyl group, preferably an aryl group, ahetero-aryl group, or a silyl group, more preferably an aryl group or ahetero-aryl group, and especially preferably represents an aryl group.

As the aryl group represented by R⁹, the preferred are phenyl,o-methylphenyl, 2,6-xylyl, and mesityl, the more preferred are phenyland mesityl, and the especially preferred is a phenyl group. Thesesubstituents may form a condensed ring structure, and these substituentsmay be bonded to each other to form a ring, e.g., biphenyl, naphthyl,anthranyl, phenanthryl, pyrenyl, naphthacenyl, etc., are exemplified.These substituents may further be substituted with other substituent.

A plurality of structures comprising carbazole and R¹ to R⁸ may bebonded to R⁹, preferably from 1 to 6 structures, more preferably from 1to 3 structures, and especially preferably from 1 to 2 structures may bebonded to R⁹.

The specific examples of the substituents represented by R⁹ to which onestructure comprising carbazole and R¹ to R⁸ is bonded are shown below,however, the invention is not restricted to these compounds. In thefollowing formulae, * is a part where the nitrogen atom of the carbazoleis to be bonded. Incidentally, the combinations of (a-0) to (k-0) (notcontaining a deuterium atom) with (1A-0) to (1Q-0) (not containing adeuterium atom) do not satisfy formula (I), but similar combinations ofboth groups other than the above satisfy formula (I).

The specific examples of the substituents represented by R⁹ to which twostructures comprising carbazole and R¹ to R⁸ are bonded are shown below,however, the invention is not restricted to these compounds. In thefollowing formulae, * is the part to which the nitrogen atom of thecarbazole is to be bonded. Incidentally, the combinations of the above(a-0) to (k-0) (not containing a deuterium atom) and the following(2A-0) to (2M-0) (not containing a deuterium atom) do not satisfyformula (I), but similar combinations of both groups other than theabove satisfy formula (I).

The specific examples of the substituents represented by R⁹ to whichthree structures comprising carbazole and R¹ to R⁸ are bonded are shownbelow, however, the invention is not restricted to these compounds. Inthe following formulae, * is the part to which the nitrogen atom of thecarbazole is to be bonded. Incidentally, the combinations of the above(a-0) to (k-0) (not containing a deuterium atom) and the following(3A-0) to (3C-0) (not containing a deuterium atom) do not satisfyformula (I), but similar combinations of both groups other than theabove satisfy formula (I).

The specific examples of the substituents represented by R⁹ to whichfour structures comprising carbazole and R¹ to R⁸ are bonded are shownbelow, however, the invention is not restricted to these compounds. Inthe following formulae, * is the part to which the nitrogen atom of thecarbazole is to be bonded. Incidentally, the combinations of the above(a-0) to (k-0) (not containing a deuterium atom) and the following(4A-0) to (4C-0) (not containing a deuterium atom) do not satisfyformula (I), but similar combinations of both groups other than theabove satisfy formula (I).

The specific example of the substituent represented by R⁹ to which sixstructures comprising carbazole and R¹ to R⁸ are bonded is shown below,however, the invention is not restricted to the compound. In thefollowing formula, * is the part to which the nitrogen atom of thecarbazole is to be bonded. Incidentally, the combinations of the above(a-0) to (k-0) (not containing a deuterium atom) and the following(6A-0) do not satisfy formula (I), but similar combinations of bothgroups other than the above satisfy formula (I).

In formula (I), at least one of R¹ to R⁹ represents a deuterium atom ora substituent containing a deuterium atom.

In the invention, the fact that at least one of R¹ to R⁹ represents adeuterium atom or a substituent containing a deuterium atom means theratio of the deuterium atom to the hydrogen atom (atom number of thedeuterium atom/atom number of the hydrogen atom) at the position wherethe deuterium atom is bonded is included in the range of from 100/0 to1/99.

This means that, as to the compound represented by formula (I), in thosethe structures of which are the same except for the hydrogen atom andthe deuterium atom, those containing the hydrogen atom and thosecontaining the deuterium atom are mixed within the above range at thespecific position.

In formula (I), the proportion of the deuterium atom to the hydrogenatom (atom number of deuterium atoms/atom number of hydrogen atoms) ispreferably contained in the range of from 100/0 to 1/99, more preferablyin the range of from 100/0 to 50/50, and especially preferably in therange of from 100/0 to 80/20.

The range of the proportion of the deuterium atom to the hydrogen atomis preferably from 100/0 to 5/95, more preferably from 100/0 to 50/50,and especially preferably from 100/0 to 80/20.

As for R¹ to R⁸, preferably one or more of R¹ to R⁸ represent adeuterium atom, more preferably two or more of R¹ to R⁸ represent adeuterium atom, and especially preferably all of R¹ to R⁸ represent adeuterium atom.

As for R¹ to R⁸, those that represent a deuterium atom are preferably R²to R⁷, more preferably R², R³, R⁶ and R⁷, and especially preferably R³and R⁶ represent a deuterium atom.

The compound represented by formula (I) is especially preferably acompound represented by formula (VIII). The compound represented byformula (VIII) will be described below.

In formula (VIII), R⁸¹ to R⁸⁸ each represents a hydrogen atom or asubstituent, and contiguous substituents of R⁸¹ to R⁸⁸ may be bonded toeach other to form a condensed ring; A represents a linking group; andn⁸¹ represents an integer of from 2 to 6. The compound represented byformula (VIII) contains at least one deuterium atom.

R⁸¹ to R⁸⁸ respectively have the same meaning as R¹ to R⁸ describedabove, and the preferred ranges are also the same. Here, thecorresponding relationship between R⁸¹ to R⁸⁸ and R¹ to R⁸ means thatthe number of units of the former is in corresponding relationship withthe number of the latter group. Other similar corresponding relationshiphas the same meaning.

n⁸¹ is preferably from 2 to 4, more preferably 2 or 3, and especiallypreferably 2.

The linking group represented by A is preferably alkylene, arylene,hetero-arylene, or silylene, more preferably arylene or hetero-arylene,and especially preferably arylene. These linking groups may further besubstituted with, e.g., the substituent represented by R¹.

The linking group represented by A also includes those described abovein (2A-0) to (6A-0) (those not containing a deuterium atom and thosecontaining a deuterium atom).

The arylene is preferably phenylene, naphthylene, biphenylene, orterphenylene, more preferably phenylene or biphenylene, and especiallypreferably phenylene.

The phenylene is preferably 1,2,3,4,5,6-hexa-substituted phenylene,1,2,4,5-tetra-substituted phenylene, 1,3,5-tri-substituted phenylene,1,2-di-substituted phenylene, 1,3-di-substituted phenylene, or1,4-di-substituted phenylene, more preferably 1,2-di-substitutedphenylene, 1,3-di-substituted phenylene, or 1,4-di-substitutedphenylene, and especially preferably 1,3-di-substituted phenylene or1,4-di-substituted phenylene. In the case of tri-substitution or highersubstitution, the substituent represented by R¹ may be substitutedbesides carbazole.

In the compound represented by formula (VIII), to contain a deuteriumatom means that the ratio of the deuterium atom to the hydrogen atom(atom number of deuterium atoms/atom number of hydrogen atoms) at theposition where the deuterium atom is bonded is included in the range offrom 100/0 to 1/99.

The range of the ratio of the deuterium atom to the hydrogen atom ispreferably from 100/0 to 5/95, more preferably from 100/0 to 50/50, andespecially preferably from 100/0 to 80/20.

The compound represented by formula (I) of the invention may be a lowmolecular weight compound, or may be an oligomer compound, or may be apolymer compound having the structure represented by formula (I) in themain chain or side chain (mass average molecular weight (in terms ofpolystyrene) is preferably from 1,000 to 5,000,000, more preferably from2,000 to 1,000,000, and still more preferably from 3,000 to 100,000).The compound represented by formula (I) is preferably a low molecularweight compound.

In the case where the compound represented by formula (I) of theinvention is an oligomer compound, or a polymer compound having thestructure represented by formula (I) in the main chain or side chain,and when the structure is contained in the main chain, it is preferredthat two or more of R¹ to R⁹ are contained, more preferably two or moreof R³, R⁶ and R⁹ are contained, and especially preferably R³ and R⁶ arecontained. When the structure is contained in the side chain, it ispreferred that any of R¹ to R⁹ is contained, more preferably any of R³,R⁶ and R⁹ is contained, and especially preferably R⁹ is contained.

In the invention, the use of the compound represented by formula (I) ofthe invention is not restricted, and may be contained in any layer ofthe organic layers. The compound represented by formula (I) of theinvention is preferably contained in any of a light-emitting layer, ahole injecting layer, a hole transporting layer, an electrontransporting layer, an electron injecting layer, an exciton blockinglayer, and a charge blocking layer, or two or more of these layers.

The compound represented by formula (I) of the invention is preferablycontained in a light-emitting layer, a hole-injecting layer or ahole-transporting layer in view of having charge of injection andtransportation of positive holes, and especially preferably contained ina light-emitting layer from the viewpoint of the stability of thematerial to the excitation state generating by recombination of thepositive holes and electrons.

It is preferred in the invention for the compound represented by formula(I) to be contained in either a light-emitting layer or the layercontiguous to the light-emitting layer, and the compound represented byformula (I) may be contained in both layers of a light-emitting layerand the layer contiguous to the light-emitting layer.

It is preferred that the compound represented by formula (I) of theinvention is contained in a light-emitting layer in an amount of from 1to 100 mass %, more preferably from 50 to 100 mass %, and still morepreferably from 80 to 100 mass %.

When the compound represented by formula (I) of the invention iscontained in layers other than a light-emitting layer, it is preferredfor the compound to be contained in an amount of from 1 to 100 mass %,more preferably from 50 to 100 mass %, and still more preferably from 80to 100 mass %.

The specific examples of the compounds represented by formula (I) areshown below, but the invention is not restricted to these compounds.

For example, exemplified compound (1-1) shows the combination of (a-1)and (2F-0), and exemplified compound (1-6) shows the combination of(a-4) and (2F-3).

The specific examples of a polymer compound and an oligomer compoundcontaining the compound represented by formula (I) are shown below, butthe invention is not restricted to these compounds. The polymer compoundmay be a homopolymer compound or may be a copolymer, and the copolymermay be any of a random copolymer, an alternating copolymer, and a blockcopolymer. In the formulae, m/n means the molar ratio of each monomercontained in the polymer, and m is an integer of from 1 to 100, n isfrom 0 to 99, and the sum of m and n is 100.

The compound containing a deuterium atom represented by formula (I) canbe synthesized according to various known methods. For example, thehydrogen atoms in the compound represented by formula (I) can beconverted to deuterium atoms using the methods disclosed inJP-A-2004-11400 and JP-A-2004-46066. Further, the compound containing adeuterium atom represented by formula (I) of the invention can besynthesized with materials containing deuterium atoms. As the materialscontaining deuterium atoms, specifically bibromobenzene-d5 (CAS No.4165-57-5), methyl iodide-d3 (CAS No. 865-50-9), resorcinol-d6 that canbe synthesized according to the method described in J. Am. Chem. Soc.,Vol. 126, No. 40, item 13033-03043 (2004), and sulfonic acid estersthereof are exemplified.

As the light-emitting material, an iridium complex phosphorescentmaterial is used in the invention, but other phosphorescent materialsmay be used in combination.

By the use of an iridium complex phosphorescent material, the effect ofthe improvement of efficiency and durability can be obtained.

As iridium complex phosphorescent materials, an iridium complexcontaining a ligand bonding to an iridium atom via carbene, an iridiumcomplex containing a ligand bonding to an iridium atom via the nitrogenatom of a pyrazole structure, and an iridium complex containing a ligandbonding to an iridium atom via the nitrogen atom of a pyridine structureare very preferred, an iridium complex containing a ligand bonding to aniridium atom via carbene and an iridium complex containing a ligandbonding to an iridium atom via the nitrogen atom of a pyrazole structureare more preferred, and an iridium complex containing a ligand bondingto an iridium atom via the nitrogen atom of a pyrazole structure isespecially preferred.

That a ligand and an iridium atom bond together means that the bondbetween the ligand and the iridium atom may be any of a covalent bond, acoordinate bond and an ionic bond.

As the carbenes to coordinate to an iridium atom, carbon monoxide, anisonitrile group and carbon carbenes stabilized with a hetero atom areexemplified.

As the iridium complex phosphorescent material containing a ligandbonding to an iridium atom via carbene, an iridium complex representedby the following formula (II) is preferred.

Formula (II) will be described below.

In formula (II), R²¹ to R²³ and R²⁵ to R²⁸ each represents a hydrogenatom or a substituent; L²¹ represents a ligand; n²² represents aninteger of from 1 to 3; n²¹ represents an integer of from 0 to 4; and Crepresents a carbene carbon coordinating to iridium.

R²¹ to R²³ and R²⁵ to R²⁸ each represents a hydrogen atom or asubstituent. The examples of the substituent include, e.g., an alkylgroup (preferably having from 1 to 30 carbon atoms, more preferably from1 to 20 carbon atoms, and especially preferably from 1 to 10 carbonatoms, e.g., methyl, ethyl, isopropyl, tert-butyl, n-octyl, n-decyl,n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc., areexemplified), an alkenyl group (preferably having from 2 to 30 carbonatoms, more preferably from 2 to 20 carbon atoms, and especiallypreferably from 2 to 10 carbon atoms, e.g., vinyl, allyl, 2-butenyl,3-pentenyl, etc., are exemplified), an alkynyl group (preferably havingfrom 2 to 30 carbon atoms, more preferably from 2 to 20 carbon atoms,and especially preferably from 2 to 10 carbon atoms, e.g., propargyl,3-pentynyl, etc., are exemplified), an aryl group (preferably havingfrom 6 to 30 carbon atoms, more preferably from 6 to 20 carbon atoms,and especially preferably from 6 to 12 carbon atoms, e.g., phenyl,p-methylphenyl, naphthyl, anthranyl, etc., are exemplified), an aminogroup (preferably having from 0 to 30 carbon atoms, more preferably from0 to 20 carbon atoms, and especially preferably from 0 to 10 carbonatoms, e.g., amino, methylamino, dimethylamino, diethylamino,dibenzylamino, diphenylamino, ditolylamino, etc., are exemplified), analkoxyl group (preferably having from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 10 carbon atoms, e.g., methoxy, ethoxy, butoxy, 2-ethylhexyloxy,etc., are exemplified), an aryloxy group (preferably having from 6 to 30carbon atoms, more preferably from 6 to 20 carbon atoms, and especiallypreferably from 6 to 12 carbon atoms, e.g., phenyloxy, 1-naphthyloxy,2-naphthyloxy, etc., are exemplified), a heterocyclic oxy group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to20 carbon atoms, and especially preferably from 1 to 12 carbon atoms,e.g., pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc., areexemplified), an acyl group (preferably having from 2 to 30 carbonatoms, more preferably from 2 to 20 carbon atoms, and especiallypreferably from 2 to 12 carbon atoms, e.g., acetyl, benzoyl, formyl,pivaloyl, etc., are exemplified), an alkoxycarbonyl group (preferablyhaving from 2 to 30 carbon atoms, more preferably from 2 to 20 carbonatoms, and especially preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonyl, ethoxycarbonyl, etc., are exemplified), anaryloxycarbonyl group (preferably having from 7 to 30 carbon atoms, morepreferably from 7 to 20 carbon atoms, and especially preferably from 7to 12 carbon atoms, e.g., phenyloxycarbonyl, etc., are exemplified), anacyloxy group (preferably having from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 10 carbon atoms, e.g., acetoxy, benzoyloxy, etc., are exemplified),an acylamino group (preferably having from 2 to 30 carbon atoms, morepreferably from 2 to 20 carbon atoms, and especially preferably from 2to 10 carbon atoms, e.g., acetylamino, benzoylamino, etc., areexemplified), an alkoxycarbonylamino group (preferably having from 2 to30 carbon atoms, more preferably from 2 to 20 carbon atoms, andespecially preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonyl-amino, etc., are exemplified), an aryloxycarbonylaminogroup (preferably having from 7 to 30 carbon atoms, more preferably from7 to 20 carbon atoms, and especially preferably from 7 to 12 carbonatoms, e.g., phenyloxycarbonylamino, etc., are exemplified), asulfonylamino group (preferably having from 1 to 30 carbon atoms, morepreferably from 1 to 20 carbon atoms, and especially preferably from 1to 12 carbon atoms, e.g., methanesulfonylamino, benzenesulfonylamino,etc., are exemplified), a sulfamoyl group (preferably having from 0 to30 carbon atoms, more preferably from 0 to 20 carbon atoms, andespecially preferably from 0 to 12 carbon atoms, e.g., sulfamoyl,methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc., areexemplified), a carbamoyl group (preferably having from 1 to 30 carbonatoms, more preferably from 1 to 20 carbon atoms, and especiallypreferably from 1 to 12 carbon atoms, e.g., carbamoyl, methylcarbamoyl,diethylcarbamoyl, phenylcarbamoyl, etc., are exemplified), an alkylthiogroup (preferably having from 1 to 30 carbon atoms, more preferably from1 to 20 carbon atoms, and especially preferably from 1 to 12 carbonatoms, e.g., methylthio, ethylthio, etc., are exemplified), an arylthiogroup (preferably having from 6 to 30 carbon atoms, more preferably from6 to 20 carbon atoms, and especially preferably from 6 to 12 carbonatoms, e.g., phenylthio, etc., are exemplified), a heterocyclic thiogroup (preferably having from 1 to 30 carbon atoms, more preferably from1 to 20 carbon atoms, and especially preferably from 1 to 12 carbonatoms, e.g., pyridylthio, 2-benzimizolylthio, 2-benzoxazolylthio,2-benzothiazolylthio, etc., are exemplified), a sulfonyl group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to20 carbon atoms, and especially preferably from 1 to 12 carbon atoms,e.g., mesyl, tosyl, etc., are exemplified), a sulfinyl group (preferablyhaving from 1 to 30 carbon atoms, more preferably from 1 to 20 carbonatoms, and especially preferably from 1 to 12 carbon atoms, e.g.,methanesulfinyl, benzenesulfinyl, etc., are exemplified), a ureido group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to20 carbon atoms, and especially preferably from 1 to 12 carbon atoms,e.g., ureido, methylureido, phenylureido, etc., are exemplified), aphosphoric acid amido group (preferably having from 1 to 30 carbonatoms, more preferably from 1 to 20 carbon atoms, and especiallypreferably from 1 to 12 carbon atoms, e.g., diethylphosphoric acidamido, phenylphosphoric acid amido, etc., are exemplified), a hydroxygroup, a mercapto group, a halogen atom (e.g., a fluorine atom, achlorine atom, a bromine atom, an iodine atom), a cyano group, a sulfogroup, a carboxyl group, a nitro group, a hydroxamic acid group, asulfino group, a hydrazino group, an imino group, a heterocyclic group(preferably having from 1 to 30 carbon atoms, and more preferably from 1to 12 carbon atoms, and as the hetero atoms, e.g., a nitrogen atom, anoxygen atom, a sulfur atom are exemplified, specifically, e.g.,imidazolyl, pyridyl quinolyl, furyl, thienyl, piperidyl, morpholino,benzoxazolyl, benzimidazolyl, benzothiazolyl, carbazolyl, azepinyl,etc., are exemplified), a silyl group (preferably having from 3 to 40carbon atoms, more preferably from 3 to 30 carbon atoms, and especiallypreferably from 3 to 24 carbon atoms, e.g., trimethylsilyl,triphenylsilyl, etc., are exemplified), a silyloxy group (preferablyhaving from 3 to 40 carbon atoms, more preferably from 3 to 30 carbonatoms, and especially preferably from 3 to 24 carbon atoms, e.g.,trimethylsilyloxy, triphenylsilyloxy, etc., are exemplified). Thesubstituents above may be further substituted.

R²¹ and R²², or R²² and R²³ may be bonded to each other to form a cyclicstructure.

The substituent represented by R²¹ is preferably an alkyl group, an arylgroup or a hetero-aryl group, more preferably an alkyl group or an arylgroup, and especially preferably a methyl group, a tert-butyl group, aphenyl group, a mesityl group, or a 2-o-xylyl group.

The substituent represented by R²² and R²³ is preferably an alkyl group,an aryl group or a hetero-aryl group, more preferably an alkyl group oran aryl group, and especially preferably a methyl group, a tert-butylgroup, or a phenyl group.

The substituent represented by R²⁵ to R²⁷ is preferably an alkyl group,an aryl group, a hetero-aryl group, a halogen group, or a cyano group,more preferably an alkyl group, an aryl group, a halogen group, or acyano group, and especially preferably a methyl group, a tert-butylgroup, a phenyl group, a fluorine atom, or a cyano group.

L²¹ represents a ligand. As the examples of ligands, the ligandsdescribed, for example, in H. Yersin, Photochemistry and Photophysics ofCoordination Compounds, Springer-Verlag (1987), and Akio Yamamoto, YukiKinzoku Kagaku—Kiso to Oyo—(Organic Metal Chemistry—Elements andApplications), Shokabo Publishing Co. (1982) are exemplified. Thepreferred ligands are halogen ligands (preferably a chlorine ligand, afluorine ligand), nitrogen-containing heterocyclic ligands (e.g.,bipyridyl, phenanthroline, phenylpyridine, pyrazolylpyridine,benzimidazolylpyridine, phenylpyrazole, picolinic acid, dipicolinicacid, etc.), diketone ligands, nitrile ligands, CO ligands, isonitrileligands, phosphorus ligands (e.g., phosphine derivatives, phosphorousacid ester derivatives, phosphinine derivatives, etc.), and carboxylicacid ligands (e.g., acetic acid ligands, etc.), and the more preferredligands are nitrogen-containing heterocyclic ligands (e.g., bipyridyl,phenanthroline, phenylpyridine, pyrazolylpyridine,benzimidazolylpyridine, and phenylpyrazole).

As the nitrogen-containing heterocyclic rings in the nitrogen-containingheterocyclic ligands, a pyridine ring, a pyrazine ring, a pyrimidinering, a pyridazine ring, a pyrrole ring, a pyrazole ring, an imidazolering, a triazole ring, a thiazole ring, an oxazole ring, an oxadiazolering, a thiadiazole ring, and an azaphosphinine ring are preferred, apyridine ring, a pyrrole ring, a pyrazole ring, and an imidazole ringare more preferred, and a pyridine ring, a pyrazole ring, and animidazole ring are still more preferred.

The nitrogen-containing heterocyclic ligands may have a substituent. Asthe examples of the substituents, the groups as described in R¹¹ aboveare exemplified, e.g., an alkyl group, an aryl group, an alkoxyl group,a fluorine atom, a cyano group, and a substituted amino group arepreferred.

n²² is preferably 2 or 3, and especially preferably 3. When n²¹ is 2 or3, a plurality of L²¹ may be the same or different. When n²² is 2 or 3,the ligand whose number is determined by n²² may be the same ordifferent.

The iridium complex phosphorescent material containing a ligand bondingto an iridium atom via carbene represented by formula (II) is morepreferably an iridium complex phosphorescent material represented by thefollowing formula (III).

Formula (III) will be described below.

In formula (III), R³¹ represents an alkyl group or an aryl group; R³⁵,R³⁶ and R³⁷ each represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group. R³⁵ and R³⁶ or R³⁶ and R³⁷ may be bonded toeach other to form a condensed ring structure. L³¹ represents a ligand,n³² represents an integer of from 1 to 3, n³¹ represents an integer offrom 0 to 4, and C represents a carbene carbon coordinating to iridium.

R³¹ represents an alkyl group or an aryl group, and more preferablyrepresents an alkyl group.

As the alkyl group represented by R³¹, a methyl group, an ethyl group, atert-butyl group, and a cyclohexyl group are preferred, a methyl groupand a tert-butyl group are more preferred, and a methyl group isespecially preferred.

As the aryl group represented by R³¹, a phenyl group, a p-methylphenylgroup, a 2-xylyl group, a 5-xylyl group, a mesityl group, a 1-naphthylgroup, a 2-naphthyl group, and an anthranyl group are preferred, aphenyl group, a p-methylphenyl group, a 2-xylyl group, a 5-xylyl group,and a mesityl group are more preferred, and a phenyl group is especiallypreferred.

R³⁵ and R²⁵, R³⁶ and R²⁶, R³⁷ and R²⁷ respectively have the samemeaning.

R³⁵ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a hydrogen atom, a fluorineatom, or a cyano group, and especially preferably represents a fluorineatom.

R³⁶ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a hydrogen atom, a fluorineatom, or a cyano group, and especially preferably represents a cyanogroup.

R³⁷ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a fluorine atom or a cyanogroup, and especially preferably represents a cyano group.

As the alkyl groups represented by R³⁵, R³⁶ and R³⁷, a methyl group, anethyl group, a tert-butyl group, a cyclohexyl group, a trifluoromethylgroup, and a perfluorobutyl group are preferred, a methyl group, atert-butyl group, a trifluoromethyl group, and a perfluorobutyl groupare more preferred, and a trifluoromethyl group is especially preferred.

As the benzo-condensed ring structure formed by R³⁵ and R³⁶, or R³⁶ andR³⁷ by bonding to each other, dibenzofuranyl, dibenzothiophenyl,N-phenylcarbazolyl, N-methylcarbazolyl, 9,9-dimethylfluorenyl,N-phenylindolyl, N-methylindolyl, benzothienyl, and 1,1-dimethylindenylare preferred, dibenzofuryl, dibenzothiophenyl, N-phenylcarbazolyl,N-methylcarbazolyl, and 9,9-dimethylfluorenyl are more preferred, anddibenzofuranyl is especially preferred.

A dibenzofuranyl structure or a dibenzothiophenyl structure formed byR³⁵ and R³⁶, or R³⁶ and R³⁷, by bonding to each other is preferably astructure bonding to an oxygen atom or a sulfur atom at the position ofR³⁵ or R³⁷, and especially preferably a structure bonding to an oxygenatom or a sulfur atom at the position of R³⁵.

L³¹ has the same meaning as that of L²¹, and the preferred range is alsothe same.

n³¹ and n²¹, and n³² and n²² respectively have the same meaning, and thepreferred ranges are also the same.

The iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyrazole structure ispreferably an iridium complex represented by the following formula (IV).

Formula (IV) will be described below.

In formula (IV), R⁴¹, R⁴², R⁴³, R⁴⁵, R⁴⁶, R⁴⁷ and R⁴⁸ each represents ahydrogen atom or a substituent; L⁴¹ represents a ligand; n⁴² representsan integer of from 1 to 3; and n⁴¹ represents an integer of from 0 to 4.

R⁴¹ to R⁴³ and R⁴⁵ to R⁴⁸ have the same meanings as those of R²¹ to R²³and R²⁵ to R²⁸ respectively.

The substituent represented by R⁴¹ to R⁴³ is preferably an alkyl group,an aryl group, or a hetero-aryl group, more preferably an alkyl group oran aryl group, and especially preferably a methyl group, a tert-butylgroup, or a phenyl group.

The substituent represented by R⁴⁵ to R⁴⁷ is preferably an alkyl group,an aryl group, a hetero-aryl group, a halogen group, or a cyano group,more preferably an alkyl group, an aryl group, a halogen group, or acyano group, and especially preferably a methyl group, a tert-butylgroup, a phenyl group, a fluorine atom, or a cyano group.

R⁴⁵ and R⁴⁶, or R⁴⁶ and R⁴⁷, may be bonded to each other to form acyclic structure.

L⁴¹ has the same meaning as that of L²¹, and the preferred range is alsothe same.

n⁴¹ and n²¹, and n⁴² and n²², respectively have the same meaning, andthe preferred ranges are also the same.

The iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyrazole structurerepresented by formula (IV) is more preferably an iridium complexphosphorescent material represented by the following formula (V).

Formula (V) will be described below.

In formula (V), R⁵² and R⁵³ each represents a hydrogen atom, an alkylgroup, or an aryl group; R⁵⁵, R⁵⁶ and R⁵⁷ each represents a hydrogenatom, a fluorine atom, an alkyl group, or a cyano group, and R⁵⁵ andR⁵⁶, or R⁵⁶ and R⁵⁷, may be bonded to each other to form a condensedring structure; L⁵¹ represents a ligand; n⁵² represents an integer offrom 1 to 3; and n⁵¹ represents an integer of from 0 to 4.

R⁵² and R⁵³ each preferably represents a hydrogen atom, an alkyl group,or an aryl group, more preferably a hydrogen atom, a methyl group, atert-butyl group, or a phenyl group, and especially preferablyrepresents a hydrogen atom.

R⁵⁵ and R³⁵, R⁵⁶ and R³⁶, R⁵⁷ and R³⁷ respectively have the samemeaning, and the preferred ranges are also the same.

L⁵¹ has the same meaning as that of L²¹, and the preferred range is alsothe same.

n⁵¹ and n²¹, and n⁵² and n²² respectively have the same meaning, and thepreferred ranges are also the same.

The iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyridine structure ispreferably an iridium complex represented by the following formula (VI).

Formula (VI) will be described below.

In formula (VI), R⁶¹ to R⁶⁸ each represents a hydrogen atom, or asubstituent; L⁶¹ represents a ligand; n⁶² represents an integer of from1 to 3; and n⁶¹ represents an integer of from 0 to 4.

R⁶¹ to R⁶³ and R⁶⁵ to R⁶⁸ have the same meanings as those of R²¹ to R²³and R²⁵ to R²⁸ respectively. R⁶⁴ has the same meaning as that of R²³.

The substituent represented by R⁶¹ to R⁶⁴ is preferably an alkyl group,an alkoxyl group, an aryloxy group, a hetero aryloxy group, or asubstituted amino group, more preferably an alkyl group, an alkoxylgroup, an aryloxy group, or a substituted amino group, and especiallypreferably a methyl group, a tert-butyl group, a methoxy group, aphenoxy group, a dimethylamino group, or a diphenylamino group.

R⁶¹ and R⁶², or R⁶² and R⁶³, or R⁶³ and R⁶⁴, may be bonded to each otherto form a cyclic structure.

The substituent represented by R⁶⁵ to R⁶⁸ is preferably an alkyl group,an aryl group, a hetero aryl group, a halogen atom, or a cyano group,more preferably an alkyl group, an aryl group, a halogen atom, or acyano group, and especially preferably a methyl group, a tert-butylgroup, a phenyl group, a fluorine atom, or a cyano group.

R⁶⁵ and R⁶⁶, or R⁶⁶ and R⁶⁷, or R⁶⁷ and R⁶⁸, may be bonded to each otherto form a cyclic structure.

L⁶¹ has the same meaning as that of L²¹, and the preferred range is alsothe same.

n⁶¹ and n²¹, and n⁶² and n²² respectively have the same meaning, and thepreferred ranges are also the same.

The iridium complex phosphorescent material containing a ligand bondingto an iridium atom via the nitrogen atom of a pyridine structurerepresented by formula (VI) is more preferably an iridium complexphosphorescent material represented by the following formula (VII).

Formula (VII) will be described below.

In formula (VII), R⁷³ represents a hydrogen atom, an alkyl group, anamino group or an alkoxyl group; R⁷⁵ to R⁷⁷ each represents a hydrogenatom, a fluorine atom, or an alkyl group; L⁷¹ represents a ligand; n⁷²represents an integer of from 1 to 3; and n⁷¹ represents an integer offrom 0 to 4.

R⁷³ preferably represents an alkyl group, an amino group, or an alkoxylgroup, more preferably a methyl group, a tert-butyl group, adimethylamino group, a diphenylamino group, a methoxy group, atert-butoxy group, or a phenoxy group, and especially preferablyrepresents a methoxy group.

R⁷⁵ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a hydrogen atom, a fluorineatom, or a cyano group, and especially preferably represents a fluorineatom.

R⁷⁶ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a hydrogen atom, a fluorineatom, or a cyano group, and especially preferably represents a cyanogroup.

R⁷⁷ preferably represents a hydrogen atom, a fluorine atom, an alkylgroup, or a cyano group, more preferably a fluorine atom, or a cyanogroup, and especially preferably represents a fluorine atom.

The alkyl group represented by R⁷⁵, R⁷⁶ and R⁷⁷ is preferably a methylgroup, an ethyl group, a tert-butyl group, a cyclohexyl group, atrifluoromethyl group, or a perfluorobutyl group, more preferably amethyl group, a tert-butyl group, a trifluoromethyl group, or aperfluorobutyl group, and especially preferably a trifluoromethyl group.

L⁷¹ has the same meaning as that of L²¹, and the preferred range is alsothe same.

n⁷¹ and n²¹, and n⁷² and n²² respectively have the same meaning, and thepreferred ranges are also the same.

The maximum emission wavelength of an iridium complex phosphorescentmaterial is the wavelength giving the greatest emission strength in themaximum value of emission spectrum. The maximum emission wavelength ispreferably from 450 to 470 nm, more preferably from 450 to 465 nm, andespecially preferably from 450 to 460 nm.

As iridium complex phosphorescent materials, the compounds described inWO 00/70655, WO 01/41512, WO 02/5645, JP-A-2002-117978, WO 04/085450, WO06/121811, WO 05/019373, WO 05/113704, WO 04/016711, and CoordinationChemistry Reviews, 250 (2006) 2093-2126 are exemplified.

The specific examples of iridium complex phosphorescent materials areshown below. However, the invention is not restricted to thesecompounds.

The complex compounds exemplified above can be manufactured, forexample, according to the process shown below.

The above metal complex compounds can be synthesized according tovarious methods, for example, the method described in G. R. Newkome etal., Journal of Organic Chemistry, 53, 786 (1988), p. 789, line 53, leftcolumn to line 7, right column, the method described on p. 790, line 18to line 38, left column, p. 790, line 19 to line 30, right column, andcombinations of these methods, and H. Lexy et al., Chemische Berichte,113, 2749 (1980), p. 2752, lines 26 to 35.

For example, the compound can be obtained by room temperature or loweror by heating a ligand or a dissociated product thereof, and a metalcompound in the presence of a solvent (e.g., a halogen-based solvent, analcohol-based solvent, an ether-based solvent, an ester-based solvent, aketone-based solvent, a nitrile-based solvent, an amide-based solvent, asulfone-based solvent, a sulfoxide-based solvent, and water areexemplified), or in the absence of a solvent, in the presence of a base(inorganic or organic various bases, e.g., sodium methoxide, potassiumt-butoxylate, triethylamine, and potassium carbonate are exemplified),or in the absence of a base.

In the invention, it is preferred to use an iridium complex as alight-emitting material, but an iridium complex may be used in layersother than a light-emitting layer.

An iridium complex is contained in a light-emitting layer in theproportion of generally from 0.1 to 50 mass % based on the amount of allthe compounds constituting the light-emitting layer, but from theviewpoint of durability and external quantum efficiency, the amount ispreferably from 1 to 50 mass %, and more preferably from 2 to 40 mass %.

Each component constituting the device of the invention will bedescribed in detail below.

Organic Electroluminescent Device:

The device of the invention will be described in detail below.

The luminescent device in the invention comprises a substrate havingthereon a cathode and an anode, and organic layers (the organic layersmay be organic layers comprising an organic compound alone, or may beorganic layers containing an inorganic compound) including an organiclight-emitting layer (hereinafter sometimes referred to as merely “alight-emitting layer”) between the electrodes. Accordingly, the organiclayer in the invention may have the constitution comprising alight-emitting layer alone. From the properties of the luminescentdevice, it is preferred that at least one electrode of the anode andcathode is transparent.

As the embodiment of lamination of the organic layers in the invention,lamination is preferably in order of a hole transporting layer, alight-emitting layer, and an electron transporting layer from the anodeside. Further, a charge blocking layer may be provided between a holetransporting layer and a light-emitting layer, or between alight-emitting layer and an electron transporting layer. A holeinjecting layer may be provided between the anode and a holetransporting layer, and an electron injecting layer may be providedbetween the cathode and an electron transporting layer. Each layer maybe divided into a plurality of secondary layers.

The constituents of the luminescent device of the invention aredescribed in detail below.

Substrate:

The substrate for use in the invention is preferably a substrate thatdoes not scatter or attenuate the light emitted from the organic layers.The specific examples of the materials of the substrate includeinorganic materials, e.g., yttria stabilized zirconia (YSZ), glass,etc., and organic materials, such as polyester, e.g., polyethyleneterephthalate, polybutylene phthalate, polyethylene naphthalate, etc.,polystyrene, polycarbonate, polyether sulfone, polyallylate, polyimide,polycycloolefin, norbornene resin, poly(chlorotrifluoroethylene), etc.

When glass is used as a substrate, non-alkali glass is preferably usedas the material for reducing elution of ions from the glass. Further,when soda lime glass is used, it is preferred to provide a barrier coatsuch as silica. In the case of organic materials, materials excellent inheat resistance, dimensional stability, solvent resistance, electricalinsulating properties and processability are preferably used.

The shape, structure and size of a substrate are not especiallyrestricted, and these can be arbitrarily selected in accordance with theintended use and purpose of the luminescent device. In general, asubstrate is preferably in a plate-like shape. The structure of asubstrate may be a single layer structure or may be a laminationstructure, and may consist of a single member or may be formed of two ormore members.

A substrate may be colorless and transparent, or may be colored andtransparent, but from the point of not scattering or attenuating thelight emitted from an organic light-emitting layer, a colorless andtransparent substrate is preferably used.

A substrate can be provided with a moisture permeation preventing layer(a gas barrier layer) on the front surface or rear surface.

As the materials of the moisture permeation preventing layer (the gasbarrier layer), inorganic materials such as silicon nitride and siliconoxide are preferably used. The moisture permeation preventing layer (thegas barrier layer) can be formed, for example, by a high frequencysputtering method.

When a thermoplastic substrate is used, if necessary, a hard coat layerand an undercoat layer may further be provided.

Anode:

An anode is generally sufficient to have the function of the electrodeto supply positive holes to an organic layer. The shape, structure andsize of an anode are not especially restricted, and these can bearbitrarily selected from known materials of electrode in accordancewith the intended use and purpose of the luminescent device. As statedabove, an anode is generally provided as a transparent anode.

As the materials of anode, for example, metals, alloys, metal oxides,electrically conductive compounds, and mixtures of these materials arepreferably exemplified. The specific examples of the materials of anodeinclude electrically conductive metal oxides, e.g., tin oxide doped withantimony or fluorine (ATO, FTO), tin oxide, zinc oxide, indium oxide,indium tin oxide (ITO), indium zinc oxide (IZO), etc., metals, e.g.,gold, silver, chromium, nickel, etc., mixtures or laminates of thesemetals with electrically conductive metal oxides, inorganic electricallyconductive substances, e.g., copper iodide, copper sulfide, etc.,organic electrically conductive materials, e.g., polyaniline,polythiophene, polypyrrole, etc., laminates of these materials with ITO,etc. Of these materials, electrically conductive metal oxides arepreferred, and ITO is especially preferred in view of productivity, highconductivity, transparency and the like.

An anode can be formed on the substrate in accordance with variousmethods arbitrarily selected from, for example, wet methods, e.g., aprinting method, a coating method, etc., physical methods, e.g., avacuum deposition method, a sputtering method, an ion plating method,etc., and chemical methods, e.g., a CVD method, a plasma CVD method,etc., taking the suitability with the material to be used in the anodeinto consideration. For example, in the case of selecting ITO as thematerial of an anode, the anode can be formed according to a directcurrent or high frequency sputtering method, a vacuum deposition method,an ion plating method, etc.

In the device in the invention, the position of the anode to be formedis not especially restricted and can be formed anywhere. The positioncan be arbitrarily selected in accordance with the intended use andpurpose of the luminescent device, but preferably provided on thesubstrate. In this case, the anode may be formed on the entire surfaceof one side of the substrate, or may be formed at a part.

As patterning in forming an anode, patterning may be performed bychemical etching such as by photo-lithography, may be carried out byphysical etching by laser, may be performed by vacuum deposition orsputtering on a superposed mask, or a lift-off method and a printingmethod may be used.

The thickness of an anode can be optionally selected in accordance withthe materials of the anode, so that cannot be regulated unconditionally,but the thickness is generally from 10 nm to 50 μm or so, and ispreferably from 50 nm to 20 μm.

The value of resistance of an anode is preferably 10³Ω/□ or less, andmore preferably 10²Ω/□ or less. In the case where an anode istransparent, the anode may be colorless and transparent, or colored andtransparent. For the coupling out of emission from the transparent anodeside, transmittance is preferably 60% or more, and more preferably 70%or more.

In connection with transparent anodes, description is found in YutakaSawada supervised, Tomei Denkyoku-Maku no Shintenkai (New Development inTransparent Electrode Films), CMC Publishing Co., Ltd. (1999), and thedescription therein can be referred to. In the case of using a plasticsubstrate low in heat resistance, a transparent anode film formed withITO or IZO at a low temperature of 150° C. or less is preferred.

Cathode:

A cathode is generally sufficient to have the function of the electrodeto supply electrons to an organic layer. The form, structure and size ofa cathode are not especially restricted, and these can be arbitrarilyselected from known materials of electrode in accordance with theintended use and purpose of the luminescent device.

As the materials of cathode, for example, metals, alloys, metal oxides,electrically conductive compounds, and mixtures of these materials areexemplified. The specific examples of the materials of cathode includealkali metals (e.g., Li, Na, K, Cs, etc.), alkaline earth metals (e.g.,Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloy,lithium-aluminum alloy, magnesium-silver alloy, indium, rare earthmetals, e.g., ytterbium, etc. These materials may be used by one kindalone, but from the viewpoint of the compatibility of stability and anelectron injecting property, two or more kinds of materials arepreferably used in combination.

As the materials constituting a cathode, alkali metals and alkalineearth metals are preferred of these materials in the point of anelectron injecting property, and materials mainly comprising aluminumare preferred for their excellent preservation stability.

The materials mainly comprising aluminum mean aluminum alone, alloys ofaluminum with 0.01 to 10 mass % of alkali metal or alkaline earth metal,or mixtures of these (e.g., lithium-aluminum alloy, magnesium-aluminumalloy, etc.).

The materials of a cathode are disclosed in detail in JP-A-2-15595 andJP-A-5-121172, and the materials described in these patents can also beused in the invention.

A cathode can be formed by known methods with no particular restriction.For example, a cathode can be formed according to wet methods, e.g., aprinting method, a coating method, etc., physical methods, e.g., avacuum deposition method, a sputtering method, an ion plating method,etc., and chemical methods, e.g., a CVD method, a plasma CVD method,etc., taking the suitability with the material constituting the cathodeinto consideration. For example, in the case of selecting metals as thematerial of a cathode, the cathode can be formed with one or two or morekinds of materials at the same time or in order by a sputtering method,etc.

Patterning in forming a cathode may be performed by chemical etchingsuch as a method by photo-lithography, may be carried out by physicaletching such as a method by laser, may be performed by vacuum depositionor sputtering on a superposed mask, or a lift-off method and a printingmethod may be used.

The position of the cathode to be formed is not especially restrictedand can be formed anywhere in the invention. The cathode may be formedon the entire surface of the organic layer, or may be formed at a part.

A dielectric layer comprising fluoride or oxide of alkali metal oralkaline earth metal may be inserted between the cathode and the organiclayer in a thickness of from 0.1 to 5 nm. The dielectric layer can beregarded as one kind of an electron injecting layer. The dielectriclayer can be formed, for example, according to a vacuum depositionmethod, a sputtering method, an ion plating method, etc.

The thickness of a cathode can be optionally selected in accordance withthe materials of the cathode, so that cannot be regulatedunconditionally, but the thickness is generally from 10 nm to 5 μm orso, and is preferably from 50 nm to 1 μm.

A cathode may be transparent or opaque. A transparent cathode can beformed by forming a thin film of the materials of the cathode in athickness of from 1 to 10 nm, and further laminating transparentconductive materials such as ITO and IZO.

Organic Layer:

Organic layers in the invention will be described below.

The device of the invention has at least one organic layer including alight-emitting layer. As organic layers other than the organiclight-emitting layer, as described above, a hole transporting layer, anelectron transporting layer, a charge blocking layer, a hole injectinglayer and an electron injecting layer are exemplified.

Formation of Organic Layers:

In the device of the invention, each layer constituting the organiclayers can be preferably formed by any of dry film-forming methods suchas a vacuum deposition method, a sputtering method, etc., a transfermethod, and a printing method.

—Light-Emitting Layer—

The light-emitting layer is a layer having functions to receive, at thetime of electric field application, positive holes from the anode, thehole-injecting layer or the hole-transporting layer, and receiveelectrons from the cathode, the electron-injecting layer or theelectron-transporting layer, and offer the field of recombination of thepositive holes and electrons to emit light. The light-emitting layer maycomprise one layer, or may be two or more layers, and in the case ofcomprising two or more layers, each layer may emit light in differentluminescent color.

The light-emitting layer in the invention may consist of alight-emitting material alone, or may comprise a mixed layer of a hostmaterial and a light-emitting material.

Here, the host material means a material other than a light-emittingmaterial of the materials constituting a light-emitting layer, andhaving at least one function of a function of dispersing alight-emitting material and maintaining the dispersion in thelight-emitting layer, a function of receiving positive holes from ananode and a hole transporting layer, a function of receiving electronsfrom a cathode and an electron transporting layer, a function oftransporting at least one of positive holes and electrons, a function ofoffering the place of recombination of positive holes and electrons, afunction of shifting the energy of exciton generated by recombination tothe light-emitting material, and a function of transporting at least oneof positive holes and electrons to the light-emitting material.

The host material is preferably a charge-transporting material. The hostmaterial may be used by one kind alone, or two or more kinds may beused. For example, the constitution of the mixture of anelectron-transporting host material and a hole-transporting hostmaterial is exemplified. Further, a material not having acharge-transporting property and not emitting light may be contained inthe light-emitting layer.

As the host material contained in the light-emitting layer in theinvention, for example, those having a carbazole structure, those havinga diarylamine structure, those having a pyridine structure, those havinga pyrazine structure, those having a triazine structure, those having anarylsilane structure, and materials described later in the items ofhole-injecting layer, hole-transporting layer, electron-injecting layer,and electron-transporting layer are exemplified.

The examples of fluorescent materials that can be used in the inventioninclude benzoxazole derivatives, benzimidazole derivatives,benzothiazole derivatives, styrylbenzene derivatives, polyphenylderivatives, diphenylbutadiene derivatives, tetraphenylbutadienederivatives, naphthalimide derivatives, coumarin derivatives, condensedaromatic compounds, perinone derivatives, oxadiazole derivatives,oxazine derivatives, aldazine derivatives, pyridine derivatives,cyclopentadiene derivatives, bisstyrylanthracene derivatives,quinacridone derivatives, pyrrolopyridine derivatives,thiadiazolopyridine derivatives, cyclopentadiene derivatives,styrylamine derivatives, diketopyrrolopyrroles derivatives, aromaticdimethylidyne compounds, various metal complexes represented by metalcomplexes of 8-quinolinol derivatives and metal complexes ofpyrromethene derivatives, polymer compounds such as polythiophene,polyphenylene, polyphenylenevinylene, etc., and compounds such asorganic silane derivatives.

The examples of phosphorescent materials that can be used alone or incombination in the invention include complexes containing a transitionmetal atom or a lanthanoid atom.

The transition metal atoms are not especially restricted, but preferablyruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium andplatinum are exemplified, and rhenium, iridium and platinum are morepreferred.

As lanthanoid atoms, lanthanum, cerium, praseodymium, neodymium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, and lutetium are exemplified. Of these lanthanoidatoms, neodymium, europium and gadolinium are preferred.

As the examples of ligands of complexes, the ligands described, forexample, in G. Wilkinson et al., Comprehensive Coordination Chemistry,Pergamon Press (1987), H. Yersin, Photochemistry and Photophysics ofCoordination Compounds, Springer-Verlag (1987), and Akio Yamamoto, YukiKinzoku Kagaku—Kiso to Oyo—(Organic Metal Chemistry—Elements andApplications), Shokabo Publishing Co. (1982) are exemplified.

As the specific examples of ligands, halogen ligands (preferably achlorine ligand), nitrogen-containing heterocyclic ligands (e.g.,phenylpyridine, benzoquinoline, quinolinol, bipyridyl, phenanthroline,etc.), diketone ligands (e.g., acetylacetone, etc.), carboxylic acidligands (e.g., acetic acid ligand, etc.), carbon monoxide ligands,isonitrile ligands, and cyano ligands are preferably exemplified, andmore preferably nitrogen-containing heterocyclic ligands areexemplified. These complexes may have one transition metal atom in acompound, or may be what is called polynuclear complexes having two ormore transition metal atoms. They may contain dissimilar metal atoms atthe same time.

As the specific examples of the light-emitting materials that can beused in combination with the iridium complex phosphorescent materials,for example, the following compounds are exemplified, but the inventionis not restricted thereto.

The phosphorescent material of the invention containing an iridiumcomplex phosphorescent material is preferably contained in thelight-emitting layer in a proportion of from 0.1 to 40 mass %, and morepreferably from 0.5 to 20 mass %. When phosphorescent materials otherthan the phosphorescent material of the invention are used incombination, the phosphorescent material of the invention is preferablycontained in the proportion of 50 mass % or more based on all the amountof the phosphorescent materials, and more preferably 80 mass % or more.

As the host material contained in the light-emitting layer in theinvention, the compound represented by formula (I) is exemplified, buthost materials other than the above compound can be used in combination.For example, other than the invention, those having a carbazolestructure, those having a diarylamine structure, those having a pyridinestructure, those having a pyrazine structure, those having a triazinestructure, those having an arylsilane structure, and the materialsdescribed later in the items of hole injecting layer, hole transportinglayer, electron injecting layer, and electron transporting layer areexemplified. Host materials capable of being used in combination arecontained in the light-emitting layer preferably in the proportion of 90mass % or less of the compound represented by formula (I), morepreferably 50 mass % or less, and especially preferably 10 mass % orless.

The thickness of the light-emitting layer is not especially limited, butis generally preferably from 1 to 500 nm, more preferably from 5 to 200nm, and still more preferably from 10 to 100 nm.

Hole Injecting Layer and Hole Transporting Layer:

The hole injecting layer and the hole transporting layer are layershaving a function to receive positive holes from the anode or anode sideand transport the positive holes to the cathode side. The hole injectinglayer and the hole transporting layer are specifically preferably thelayers containing carbazole derivatives, triazole derivatives, oxazolederivatives, oxadiazole derivatives, imidazole derivatives,polyarylalkane derivatives, pyrazoline derivatives, pyrazolonederivatives, phenylenediamine derivatives, arylamine derivatives,amino-substituted chalcone derivatives, styrylanthracene derivatives,fluorenone derivatives, hydrazone derivatives, stilbene derivatives,silazane derivatives, aromatic tertiary amine compounds, styrylaminecompounds, aromatic dimethylidyne compounds, porphyrin compounds,organic silane derivatives, carbon, and various kinds of metal complexesrepresented by Ir complex having phenylazole or phenylazine as theligand.

The thickness of each of the hole injecting layer and the holetransporting layer is preferably 500 nm or less from the viewpoint oflowering driving voltage.

The thickness of the hole transporting layer is preferably from 1 to 500nm, more preferably from 5 to 200 nm, and still more preferably from 10to 100 nm. The thickness of the hole injecting layer is preferably from0.1 to 200 nm, more preferably from 0.5 to 100 nm, and still morepreferably from 1 to 100 nm.

The hole injecting layer and the hole transporting layer may be a singlelayer structure comprising one or two or more of the above materials, ormay be a multilayer structure comprising a plurality of layers of thesame or different compositions.

Electron Injecting Layer and Electron Transporting Layer:

The electron injecting layer and the electron transporting layer arelayers having a function to receive electrons from the cathode or thecathode side and transport the electrons to the anode side. The electroninjecting layer and the electron transporting layer are specificallypreferably layers containing triazole derivatives, oxazole derivatives,oxadiazole derivatives, imidazole derivatives, fluorenone derivatives,anthraquinodimethane derivatives, anthrone derivatives, diphenylquinonederivatives, thiopyran dioxide derivatives, carbodiimide derivatives,fluorenylidene-methane derivatives, distyrylpyrazine derivatives,aromatic ring tetracarboxylic acid anhydride such as naphthalene,perylene, etc., phthalocyanine derivatives, various metal complexesrepresented by metal complexes of 8-quinolinol derivatives, metalcomplexes having metalphthalocyanine, benzoxazole, or benzothiazole asthe ligand, organic silane derivatives, and the like.

The thickness of each of the electron injecting layer and the electrontransporting layer is preferably 500 nm or less from the viewpoint oflowering driving voltage.

The thickness of the electron transporting layer is preferably from 1 to500 nm, more preferably from 5 to 200 nm, and still more preferably from10 to 100 nm. The thickness of the electron injecting layer ispreferably from 0.1 to 200 nm, more preferably from 0.2 to 100 nm, andstill more preferably from 0.5 to 50 nm.

The electron injecting layer and the electron transporting layer may bea single layer structure comprising one or two or more of the abovematerials, or may be a multilayer structure comprising a plurality oflayers of the same or dissimilar compositions.

Hole Blocking Layer:

The hole blocking layer is a layer having a function of preventing thepositive holes transported from the anode side to the light-emittinglayer from passing through to the cathode side. In the invention, a holeblocking layer can be provided as the organic layer contiguous to thelight-emitting layer on the cathode side.

As the examples of the organic compounds constituting the hole blockinglayer, aluminum complexes, e.g., BAlq, triazole derivatives,phenanthroline derivatives, e.g., BCP, can be exemplified.

The thickness of the hole blocking layer is preferably from 1 to 500 nm,more preferably from 5 to 200 nm, and still more preferably from 10 to100 nm.

The hole blocking layer may be a single layer structure comprising oneor two or more of the above materials, or may be a multilayer structurecomprising a plurality of layers of the same or dissimilar compositions.

Protective Layer:

In the invention the organic EL device may be completely protected witha protective layer.

It is sufficient for the materials to be contained in the protectivelayer to have a function capable of restraining the substancesaccelerating deterioration of the device, e.g., water, oxygen, etc.,from entering the device.

The specific examples of such materials include metals, e.g., In, Sn,Pb, Au, Cu, Ag, Al, Ti, Ni, etc., metal oxides, e.g., MgO, SiO, SiO₂,Al₂O₃, GeO, NiO, CaO, BaO, Fe₂O₃, Y₂O₃, TiO₂, etc., metal nitrides,e.g., SiN_(x), SiN_(x)O_(y), etc., metal fluorides, e.g., MgF₂, LiF,AlF₃, CaF₂, etc., polyethylene, polypropylene, polymethyl methacrylate,polyimide, polyurea, polytetrafluoroethylene,polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymers ofchlorotrifluoroethylene with dichlorodifluoroethylene, copolymersobtained by copolymerization of monomer mixtures containingtetrafluoroethylene and at least one comonomer, fluorine-containingcopolymers having a cyclic structure on the main chain of the copolymer,water absorptive substances having a water absorption rate of not lowerthan 1%, moisture proofing substances having a water absorption rate ofnot higher than 0.1%.

The forming method of the protective layer is not especially restrictedand, for example, a vacuum deposition method, a sputtering method, areactive sputtering method, an MBE (molecular beam epitaxy) method, acluster ion beam method, an ion plating method, a plasma polymerizationmethod (a high frequency excitation ion plating method), a plasma CVDmethod, a laser CVD method, a heat CVD method, a gas source CVD method,a coating method, a printing method, a transfer method, etc., can beapplied to the invention.

Sealing Container:

The device of the invention may be completely sealed in a sealingcontainer.

Further, a water absorber or an inert liquid may be filled in the spacebetween the sealing container and the luminescent device. The waterabsorber is not especially restricted and, for example, barium oxide,sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calciumsulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride,magnesium chloride, copper chloride, cesium fluoride, niobium fluoride,calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesiumoxide, etc., can be exemplified. The inert liquid is not particularlylimited and, for example, paraffins, liquid paraffins, fluorinesolvents, such as perfluoroalkane, perfluoroamine, perfluoroether, etc.,chlorine solvents, and silicone oils are exemplified.

Driving Method:

Emission can be obtained by the application of DC (if necessary, analternating current factor may be contained) voltage (generally from 2to 15 V) or direct electric current between the anode and cathode of thedevice of the invention.

In connection with the driving methods of the device of the invention,the driving methods disclosed in JP-A-2-148687, JP-A-6-301355,JP-A-5-29080, JP-A-7-134558, JP-A-8-234685, JP-A-8-241047, JapanesePatent 2784615, and U.S. Pat. Nos. 5,828,429 and 6,023,308 can beapplied to the invention.

EXAMPLE

Others:

The device in the invention can be preferably used in display devices,displays, backlights, electrophotography, illumination light sources,recording light sources, exposure light sources, reading light sources,indicators, signboards, interior designs, optical communications, andthe like.

Example

The invention will be described in detail with reference to examples,but the invention should not be construed as being restricted thereto.

Synthesis of Exemplified Compounds:

Exemplified Compound (1-3) can be synthesized by the use of carbazolecontaining a deuterium atom on 1- to 8-positions described inHeterocycles, Vol. 67, No. 1, 353-359 (2006), by coupling with4,4′-dibromobiphenyl by using a palladium catalyst and a coppercatalyst.

Exemplified Compound (4-3) can be synthesized by coupling with1,3-dibromobenzene in the same manner as in exemplified Compound (1-3).

Exemplified Compound (12-3) can be synthesized by coupling with3,6-dibromo-9-phenylcarbazole described in Tetrahedron, Vol. 54, No. 42,12707-12714 (1998) in the same manner as in exemplified Compound (1-3).

Exemplified Compound (4-6) can be synthesized according to the followingmethod.

Resorcinol-d6 can be synthesized according to the method described in J.Am. Chem. Soc., Vol. 126, No. 40, 13033-03043 (2004).

Resorcinol-d6 (4.6 g) and triethylamine (14 ml) are mixed in dehydratedacetonitrile (40 ml). While cooling the reaction vessel in a water bath,nonafluorobutanesulfonyl fluoride (15.5 ml) is added. After stirring thereaction mixture at room temperature for 3 hours, water is added, andthe organic layer is extracted from the reaction solution with a mixedsolvent of hexane-ethyl acetate. The organic layer extracted is washedwith dilute hydrochloric acid, water and saturated brine in this order,dried with sodium sulfate anhydride, and then the solvent is distilledoff under reduced pressure to obtain 25.9 g of a crude product ofintermediate A.

The crude product of intermediate A (13.6 g), carbazole-d8 (7.0 g),bis(benzylideneacetone) palladium (0.56 g), XantPhos (CAS No.161265-03-8, 1.16 g), and rubidium carbonate (23 g) are mixed in toluene(200 ml) in nitrogen atmosphere, and the mixture is refluxed withheating. After the elapse of 8 hours, bis(benzylideneacetone) palladium(0.28 g) is additionally added, and the reaction mixture is refluxedwith heating for further 3 hours. After cooling the reaction mixture toroom temperature, water and ethyl acetate are added to the reactionmixture, and an organic layer obtained by filtering the insoluble matteris washed with water and saturated brine, and dried with sodium sulfateanhydride. A crude product obtained by the concentration of the organiclayer under reduced pressure is purified by silica gel columnchromatography (a mixed eluent of hexane/ethyl acetate having a volumeratio of 20), and further subjected to recrystallization and sublimationpurification to obtain 2.7 g of exemplified Compound (4-6).

The degree of conversion to deuterium of exemplified Compound (4-6)measured by ¹H-NMR with 1,2-dibromobutane as the internal standardsubstance, and heavy chloroform and heavy dimethyl sulfoxide as thesolvents is 96% at every position.

In the above manufacturing method, when a defined substituent changesunder the condition of a certain synthesizing method, or when it is notsuitable to perform the method, the manufacture is easily possible bythe means such as protection or de-protection of the functional groups(for example, T. W. Greene, Protective Groups in Organic Synthesis, JohnWiley & Sons Inc. (1981)). Further, if necessary, it is also possible toarbitrarily change the order of the reaction processes such as theintroduction of substituents and the like.

Manufacture and Evaluation of Organic Electroluminescent Device:

(1) Manufacture of Organic Electroluminescent Device in ComparativeExample 1

A glass substrate having an ITO film having a thickness of 0.5 mm and2.5 cm square (manufactured by Geomatec Co., Ltd., surface resistance:10Ω/□) is put in a washer and subjected to ultrasonic washing in2-propanol, and then UV-ozone treatment for 30 minutes. The followingorganic layers are deposited in order on the transparent anode (ITOfilm) by vacuum deposition.

The deposition speed in the examples of the invention is 0.2 nm/secunless otherwise indicated. The deposition speed is measured with aquartz oscillator film formation controller, CRTM-9000 (manufactured byULVAC, Inc.). The film thickness of each film shown below is alsocomputed from the calibration curves formed from the numeric value ofCRTM-9000 and the thickness measured with a Dektak feeler type thicknessmeter.

<1> Compound A: Film thickness: 80 nm

<2> Compound B: Film thickness: 10 nm

<3> Co-deposition of Comparative Compound 1+light-emitting material A(10 wt %): Film thickness: 60 nm

<4> Compound C: Film thickness: 10 nm

<5> Compound D: Film thickness: 30 nm

Finally, lithium fluoride of 0.1 nm and metal aluminum are deposited inthis order in a thickness of 100 nm to prepare a cathode. This is put ina glove box replaced with argon gas so as not to be in contact with theair, and sealed with a stainless steel sealing can and a UV-curing typeadhesive (XNR5516HV, manufactured by Nagase Ciba) to thereby obtain anorganic electroluminescent device in Comparative Example 1.

(2) Manufacture of Organic Electroluminescent Devices in ComparativeExamples 2 to 8 and Examples 1 to 8

Organic electroluminescent devices in Comparative Examples 2 to 8 andExamples 1 to 8 are manufactured according to the same manner as inComparative Example 1 except for changing, as shown in Table 1 below,light-emitting material A to light-emitting materials B to H having thestructures shown below, Comparative Compound 1 to Comparative Compound2, exemplified Compound (1-3) and exemplified Compound (4-6) shownbelow.

The chemical structures of Compounds A to D are shown below.

The chemical structures of light-emitting materials A to H and emissionwavelengths in a state of solution are as follows.

The chemical structures of Comparative Compounds 1 to 3 are shown below.

The chemical structures of exemplified Compounds (1-3) and (4-6) areshown below.

The obtained organic electroluminescent devices are evaluated accordingto the following methods.

(1) Measurement of Driving Voltage

Each of the organic electroluminescent devices is set on an emissionspectrum measuring system, ELS1500 (manufactured by ShimadzuCorporation), and the applied voltage is measured when the luminance is100 Cd/m².

(2) Evaluation of Driving Durability

Each of the organic electroluminescent devices is set on OLED testsystem ST-D type (manufactured by TSK Co.), and the device is driven onthe condition of normal direction constant current of 0.4 mA by constantcurrent mode, and half life of luminance (time required for luminance tolower to 50% from the initial luminance) is found.

The results of evaluations of organic electroluminescent devices are asshown in Table 1 below. As for driving voltage and half life time ofluminance, the results of Example are shown in a relative value with theresults of Comparative Example as 100 in the combination of Example andComparative Example using the same light-emitting material.

TABLE 1 Half Life Material to be Driving Time of Deposited with Voltagein Luminance Example Light-Emitting Light-Emitting Relative in RelativeNo. Material Material Value Value Comparative Light-Emitting Comparative100 100 Example 1 Material A Compound 1 Example 1 Light-EmittingExemplified 95 110 Material A Compound (1-3) Comparative Light-EmittingComparative 100 100 Example 2 Material B Compound 1 Example 2Light-Emitting Exemplified 97 115 Material B Compound (1-3) ComparativeLight-Emitting Comparative 100 100 Example 3 Material C Compound 2Example 3 Light-Emitting Exemplified 95 112 Material C Compound (4-6)Comparative Light-Emitting Comparative 100 100 Example 4 Material DCompound 2 Example 4 Light-Emitting Exemplified 90 140 Material DCompound (4-6) Comparative Light-Emitting Comparative 100 100 Example 5Material E Compound 2 Example 5 Light-Emitting Exemplified 92 135Material E Compound (4-6) Comparative Light-Emitting Comparative 100 100Example 6 Material F Compound 2 Example 6 Light-Emitting Exemplified 90160 Material F Compound (4-6) Comparative Light-Emitting Comparative 100100 Example 7 Material G Compound 2 Example 7 Light-Emitting Exemplified80 210 Material G Compound (4-6) Comparative Light-Emitting Comparative100 100 Example 8 Material H Compound 2 Example 8 Light-EmittingExemplified 85 180 Material H Compound (4-6)

From the above results, the organic electroluminescent devices of theinvention using the compounds represented by formula (I) and iridiumcomplex phosphorescent materials in combination have conspicuous effectand, in particular, the shorter the light-emitting wavelength of thelight-emitting material in combination, the more conspicuous is theeffect.

(2) Manufacture and Evaluation of Organic Electroluminescent Devices inComparative Examples 2-1 to 2-13 and Examples 2-1 to 2-7

The devices in Comparative Examples 2-1 to 2-13 and Examples 2-1 to 2-7are manufactured in the same manner as in Comparative Example 1 andevaluated in the same manner except for changing the light-emittingmaterial A and comparative compound 1 in the device in ComparativeExample 1 to the combinations of the light-emitting materials andmaterials to be co-deposited with the light-emitting materials (hostmaterials) shown in Table 2 below. The results obtained are shown inTable 2. However, the devices in Comparative Example 2-5* and Example2-5** have a layer containing comparative compound 3 having a thicknessof 3 nm and a layer containing exemplified compound (12-2) having athickness of 3 nm respectively between the layer containing compound Band the layer containing comparative compound 1 in Comparative Example1.

TABLE 2 Half Life Time of Material to Be Co-deposited with DrivingVoltage Luminance in Example No. Light-Emitting Material Light-EmittingMaterial in Relative Value Relative Value Comparative Example 2-1Light-Emitting Material E Comparative Compound 4 100 100 Example 2-1Light-Emitting Material E Exemplified Compound (2-3) 95 140 ComparativeExample 2-2 Light-Emitting Material E Comparative Compound 5 100 100Example 2-2 Light-Emitting Material E Exemplified Compound (3-1) 98 130Comparative Example 2-3 Light-Emitting Material E Comparative Compound 6100 100 Example 2-3 Light-Emitting Material E Exemplified Compound (5-3)90 135 Comparative Example 2-4 Light-Emitting Material G ComparativeCompound 7 100 100 Example 2-4 Light-Emitting Material G ExemplifiedCompound (8-2) 98 200 Comparative Example 2-5* Light-Emitting Material GComparative Compound 7 100 100 Example 2-5** Light-Emitting Material GExemplified Compound (8-2) 95 220 Comparative Example 2-6 Light-EmittingMaterial G Comparative Compound 8 100 100 Example 2-6 Light-EmittingMaterial G Exemplified Compound (9-5) 89 190 Comparative Example 2-7Light-Emitting Material G Comparative Compound 9 100 100 Example 2-7Light-Emitting Material G Exemplified Compound (14-3) 87 195 ComparativeExample 2-8 Light-Emitting Material I Comparative Compound 1 100 100Comparative Example 2-9 Light-Emitting Material I Exemplified Compound(1-3) 98 110 Comparative Example 2-10 Light-Emitting Material JComparative Compound 4 100 100 Comparative Example 2-11 Light-EmittingMaterial J Exemplified Compound (2-3) 95 105 Comparative Example 2-12Light-Emitting Material K Comparative Compound 2 100 100 ComparativeExample 2-13 Light-Emitting Material K Exemplified Compound (4-1) 97 103*Having a layer containing comparative compound 3 having a thickness of3 nm. **Having a layer containing exemplified compound (12-2) having athickness of 3 nm.

The chemical structures of light-emitting materials I to K are as shownbelow.

The chemical structures of comparative compounds 4 to 9 are as shownbelow.

From the results shown in Table 2, in the embodiment of combining thecompounds represented by formula (I) and iridium complex phosphorescentmaterials, the organic electroluminescent devices in the invention haveespecially conspicuous effect, and also have the effect even when usedin the layer other than the light-emitting layer.

(3) Manufacture and Evaluation of Organic Electroluminescent Devices inComparative Examples 3-1 and 3-2 and Examples 3-1 and 3-2

The devices in Comparative Examples 3-1 and 3-2 and Examples 3-1 and 3-2are manufactured in the same manner as in Comparative Example 1 andevaluated in the same manner except for changing compound B andcomparative compound 1 in the device in Comparative Example 1 to thematerials shown in Table 3 below. The results obtained are shown inTable 3.

TABLE 3 Driving Half Life Time Layer of Voltage in of LuminanceLuminescent Layer of Comparative Relative in Relative Device Compound BCompound 1 Value Value Comparative Comparative Comparative 100 100Example 3-1 Compound 5 Compound 1 Example 3-1 Exemplified Comparative 97130 Compound Compound 1 (3-3) Comparative Comparative Comparative 100100 Example 3-2 Compound 5 Compound 1 Example 3-2 ExemplifiedExemplified 89 205 Compound Compound (3-3) (1-3)

From the results in Table 3, it is seen that the effect of the inventioncan also be obtained by using the compound represented by formula (I) inthe organic layer contiguous to the light-emitting layer, and especiallyconspicuous effect can be obtained by using the compound represented byformula (I) in each of the light-emitting layer and the organic layercontiguous to the light-emitting layer.

(4) Manufacture and Evaluation of Organic Electroluminescent Devices inComparative Examples 4-1 and 4-2

The devices in Comparative Examples 4-1 and 4-2 are manufactured in thesame manner as in Comparative Example 1 and evaluated in the same mannerexcept for changing comparative compound 1 and compound C used in theorganic electroluminescent device in Comparative Example 1 to thematerials shown in Table 4 below. The results obtained are shown inTable 4.

TABLE 4 Driving Half Life Time Layer of Voltage in of LuminanceLuminescent Comparative Layer of Relative in Relative Device Compound 1Compound C Value Value Comparative Comparative Compound C 100 100Example 4-1 Compound 2 Comparative Comparative Compound E 98 103 Example4-2 Compound 2

The chemical structure of compound E is as shown below.

In Table 4, there is almost no difference in the effects in drivingvoltage and in half life time of luminance in the case of using compoundC and in the case of using compound E obtained by deuterating compoundC.

The results in Tables 1 and 4 show that the effect of the invention isnot obtained by deuteration of a compound but is a peculiar effectobtained by using the compound represented by formula (I) having aspecific structure and containing a deuterium atom.

The invention can provide an organic electroluminescent device excellentin efficiency (electric power consumption) and durability.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

What is claimed is:
 1. An organic electroluminescent device comprising:a pair of electrodes; and an organic layer between the pair ofelectrodes, which comprises a light-emitting layer, wherein the organiclayer contains a compound represented by the following formula (I); andthe light-emitting layer contains an iridium complex phosphorescentmaterial:

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each represents a hydrogenatom or a substituent, and contiguous substituents of R¹ and R², R² andR³, R³ and R⁴, R⁴ and R⁵, R⁵ and R⁶, R⁶ and R⁷, or R⁷ and R⁸ may bebonded to each other to form a condensed ring; R⁹ represents an alkylgroup, an alkenyl group, an aryl group, a hetero-aryl group, or a silylgroup, and each of which group may be substituted with a substituent;and at least one of R¹ to R⁹ represents a deuterium atom or asubstituent containing a deuterium atom.
 2. The organicelectroluminescent device of claim 1, wherein the iridium complexphosphorescent material has a maximum emission wavelength of smallerthan 470 nm.
 3. The organic electroluminescent device of claim 1,wherein the iridium complex phosphorescent material contains a ligandbonding to an iridium atom via a carbene carbon.
 4. The organicelectroluminescent device of claim 3, wherein the iridium complexphosphorescent material containing a ligand bonding to an iridium atomvia a carbene carbon is represented by the following formula (II):

wherein R²¹, R²², R²³, R²⁵, R²⁶, R²⁷ and R²⁸ each represents a hydrogenatom or a substituent; L²¹ represents a ligand; n²² represents aninteger of from 1 to 3; n²¹ represents an integer of from 0 to 4; and Crepresents the carbene carbon coordinating to the iridium atom.
 5. Theorganic electroluminescent device of claim 4, wherein the iridiumcomplex phosphorescent material containing a ligand bonding to aniridium atom via a carbene carbon is represented by the followingformula (III):

wherein R³¹ represents an alkyl group or an aryl group; R³⁵, R³⁶ and R³⁷each represents a hydrogen atom, a fluorine atom, an alkyl group, or acyano group, and R³⁵ and R³⁶ or R³⁶ and R³⁷ may be bonded to each otherto form a condensed ring structure; L³¹ represents a ligand; n³²represents an integer of from 1 to 3; n³¹ represents an integer of from0 to 4; and C represents the carbene carbon coordinating to the iridiumatom.
 6. The organic electroluminescent device of claim 1, wherein theiridium complex phosphorescent material contains a ligand bonding to aniridium atom via a nitrogen atom of a pyrazole structure.
 7. The organicelectroluminescent device of claim 6, wherein the iridium complexphosphorescent material containing a ligand bonding to an iridium atomvia a nitrogen atom of a pyrazole structure is represented by thefollowing formula (IV):

wherein R⁴¹, R⁴², R⁴³, R⁴⁵, R⁴⁶, R⁴⁷ and R⁴⁸ each represents a hydrogenatom or a substituent; L⁴¹ represents a ligand; n⁴² represents aninteger of from 1 to 3; and n⁴¹ represents an integer of from 0 to
 4. 8.The organic electroluminescent device of claim 7, wherein the iridiumcomplex phosphorescent material containing a ligand bonding to aniridium atom via a nitrogen atom of a pyrazole structure is representedby the following formula (V):

wherein R⁵² and R⁵³ each represents a hydrogen atom, an alkyl group, oran aryl group; R⁵⁵, R⁵⁶ and R⁵⁷ each represents a hydrogen atom, afluorine atom, an alkyl group, or a cyano group, and R⁵⁵ and R⁵⁶ or R⁵⁶and R⁵⁷ may be bonded to each other to form a condensed ring structure;L⁵¹ represents a ligand; n⁵² represents an integer of from 1 to 3; andn⁵¹ represents an integer of from 0 to
 4. 9. The organicelectroluminescent device of claim 1, wherein the iridium complexphosphorescent material contains a ligand bonding to an iridium atom viathe nitrogen atom of a pyridine structure.
 10. The organicelectroluminescent device of claim 9, wherein the iridium complexphosphorescent material containing a ligand bonding to an iridium atomvia the nitrogen atom of a pyridine structure is represented by thefollowing formula (VI):

wherein R⁶¹, R⁶², R⁶³, R⁶⁴, R⁶⁵, R⁶⁶, R⁶⁷ and R⁶⁸ each represents ahydrogen atom or a substituent; L⁶¹ represents a ligand; n⁶² representsan integer of from 1 to 3; and n⁶¹ represents an integer of from 0 to 4.11. The organic electroluminescent device of claim 10, wherein theiridium complex phosphorescent material containing a ligand bonding toan iridium atom via the nitrogen atom of a pyridine structure isrepresented by the following formula (VII):

wherein R⁷³ represents a hydrogen atom, an alkyl group, an amino group,or an alkoxyl group; R⁷⁵, R⁷⁶ and R⁷⁷ each represents a hydrogen atom, afluorine atom, a cyano group, or an alkyl group; L⁷¹ represents aligand; n⁷² represents an integer of from 1 to 3; and n⁷¹ represents aninteger of from 0 to
 4. 12. The organic electroluminescent device ofclaim 1, wherein the compound represented by formula (I) is representedby the following formula (VIII):

wherein R⁸¹, R⁸², R⁸³, R⁸⁴, R⁸⁵, R⁸⁶, R⁸⁷ and R⁸⁸ each represents ahydrogen atom or a substituent, and contiguous substituents of R⁸¹ andR⁸², R⁸² and R⁸³, R⁸³ and R⁸⁴, R⁸⁴ and R⁸⁵, R⁸⁵ and R⁸⁶, R⁸⁶ and R⁸⁷, orR⁸⁷ and R⁸⁸ may be bonded to each other to form a condensed ringstructure; A represents a linking group; and n⁸¹ represents an integerof from 2 to 6; and the compound represented by the formula (VIII)contains at least one deuterium atom.
 13. The organic electroluminescentdevice of claim 1, wherein the compound represented by the formula (I)is contained in the light-emitting layer.
 14. The organicelectroluminescent device of claim 1, wherein the light emitting layercontains the iridium complex and the compound of Formula I.
 15. Theorganic electroluminescent device of claim 10, wherein at least one of(a)-(c) is true: (a) n⁶² is 1 or 2; (b) at least one of R⁶¹-R⁶⁸ is asubstituent; (c) any two adjacent of R⁶¹-R⁶⁸ join to form a ring.